Several meter calibration error analysis
Woltman water meter,Standard containers fraction tolerances allow relative standard uncertainty u = 0.002 / 3 = 0.00067 per thousand standard containers indicative scale resolution, the relative standard uncertainty u superscript = 0.001 / 3 = 0.00058
15 to 25 meter pointer minimum resolution of 0.05 liters, check if water consumption is 10 liters a relative resolution is 0.005,
Relative standard uncertainty uw = 0.0025 min / 3 = 0.00144
The relative combined standard uncertainty uc = 0 .00067 2 0. 00058 2 0. 00144 2 = 0.0017
Standard relative expanded uncertainty U99 = 3 × 0.0017 = 0.51%
2.2 commutated static weighing method.
Commutated static weighing method is an indirect measurement, methods of operation as follows: clamping meter, exhaust, regulate the flow of traffic to check the operation when the meter uniform rotation at the flow rate of the commutator so check into the flow transducer weighing vessel operating commutator swapped out traffic light at the same time in the process water meter record electrical signal indicative of the quality of the electronic scale shown by the equation V = m / ρ in terms of volume when the water reached the standard requirements .Woltman water meter
m- ρ- mass density of water
Meter structure, the surrounding environment will sometimes photoelectric signal recording meter indication value interfere, generating gross error.
2.2.1 System Error
1) When calculating the density difference between the density of water and set the actual use of water can be seen from Table 3, the difference between the two is about 0.2%, ranging from around room temperature, have different density different checksum water
The degree of difference in the actual operation is difficult to determine.
2) commutator mounting position and reversing time difference error caused by air buoyancy.
2.2.2 random error
1) In the crystal frequency is based on the timing clock resolution
2) electronic scale reading Resolution
2.2.3 The main items uncertainty calculation
If an electronic scales weighing the relative tolerance within a range of 0.002 to 0.001 relative resolution: tolerance relative standard uncertainty U allow = 0.002 / 3 = 0.00067 resolution relative standard uncertainty U = 0.001 points / 3 = 0.00058
The relative combined standard uncertainty uc = 0. 00067 2 0. 00058 2 = 0.00089
Standard relative expanded uncertainty U99 = 3 × 0.00089 = 0.27%
2.3 piston cylinder dynamic volumetric method
Piston cylinder dynamic volumetric method is a direct calibration method, the servo motor drive screw pushes the piston in the cylinder to move the accuracy of the volume depends on the screw, cylinder measurement accuracy and precision, distance and speed of movement determine the volume and flow. Proceed as follows: clamping meter, exhaust, uniform rotation when the meter start recording at checking the flow through the piston moves in the cylinder volume at the same time light signals indicating the recording meter, standard volume V = π / 4 × rtD2, flow rate Q = π / 4 × ntD2.woltman water meter
r- number of motor revolutions